Impulse sending mechanism



March 17, 1942 c. R. WOODLAND-ET AL Y 2,276,444

IMPULSE SENDING. MECHANISM Filed Sept. 8, 1939 6 Sheets-Sheetl NVE-NTOR5 CECN. ROBERT WOODLAND JOHN WILLIAM MCLEW N o T H GZ U 0 H E N m K a E March 17, 1942. g, WOODLAND ETAL 2,276,444

IMPULSE SENDING MECHANISM Filed Sept. 8, 1939 6 Sheets-Sheet 2 \NVENTORS CECIL ROBERT WOOPLAND JOHN wmuam M usw Bk": muss HOUQHTON March 1942- c. R. WOODLAND ETAL 2,276,444

' IMPULSE SENDING MECHANISM Filed Sept. 8, 1939 6 Sheets-Sheet 3 I Ll] \NvEN-ro as cEc\\ ROBERT WOODLAND JONN WILLIAM MCLEW ER\C \NNE HOUQHTON BY% Z.

March 17, 1942. c. R. WOODLAND EI'AL 2,275,444

IMPULSE SENljING MECHANISM Filed Sept. 8, 1939 6 Sheets-Sheet 4 KDQ Y VA 2 'W 1 INVENTORS CECIL ROBERT WOODLAND JOHN wuLLmm M: CLEW ER: s HOUGHTON March 17, 1942; c, WQQDLAND ErAL 2,276,444

IMPULSE SENDING MECHANISM Filed se tl 8, 1939 G'Sheejzs-Sheet 5 IMP f-I' w H PH. a c

I smw 5T \NVENTORS CECIL ROBERT WOODLAND JOHN W\L\.\AM M cLEw Ema \NNES HOUQHTON March 17, 1942. c. R. NWOODLAND l. 2,276,444-

IMPULSE SENDING MECHANISM Filed Sept 8, 1939 6 Sheets-$heet 6 \NVENTORS CECJL. ROBERT WOODLAND JOHN WILUAM M CLEW ERlC \NNES HOUGHTON Patented Mar. 17, 1942 IMPULSE SENDING MECHANISM Cecil Robert Woodland, John William McClew, and Eric Innes Houghton, Liverpool, England, assignors to Associated Telephone & Telegraph Company, Chicago, Ill., a corporation of Delaware Application September 8, 1939, Serial No. 293,988 In Great Britain September 28, 1938 Claims.

The present invention relates to key-operated impulse senders for use more particularly in telephone or like signalling systems.

Both entirely mechanical and entirely electrical key senders are known and these types have their advantages and disadvantages. For instance, the mechanical keysender is cheap and occupies only a small mounting space but cannot be located a distance from the digit keys. The scope of application of this type of keysender is therefore limited to cases where keysenders are to be provided on an individual rather than a common basis, for instance, on the operators position of a small P. B. X board. Furthermore with the mechanical type it is difiicult to arrange for the withholding of the transmission of the keyed digits until all digits of a number have been set up and this requirement is generally desirable. On the other hand the electrical type will meet all the operating requirements involved but it has the disadvantage of being both costly and bulky.

The general object of the invention is to provide a simple and efiicient electro-mechanical keysender which combines the operating advantages of the purely electrical keysender with the cheapness and compactness of the purely mechanical keysender.

In McClew and Woodlands Patent 2,188,461, issued January 30, 1940, there is described an electro-mechanical device for repeating and regenerating received impulses. Such a device is known as a mechanical impulse repeater and the length of the train ,of impulses transmitted thereby is determined by a mechanical marking corresponding to the received train rather than by an electrical marking as is more usual. It is a further object of the invention to adapt a mechanical impulse repeater of this type for operation under the control of digit keys.

According to one feature of the invention, the seting of the mechanical impulse repeater is effected by controlling the permissible amount of movement of a member in accordance with the digit key which has been operated. The movement of the member in turn controls the displacement of the pin-setting lever of the mechanical impulse repeater so that the latter is displaced to an extent which depends on whichever digit key has been depressed.

In one embodiment according to the invention the depression of a key is efiective in causing the energising of an electromagnet to cause a stop to advance into the path of movement of the member to limit the movement of the latter to an extent corresponding to the key which has been depressed. The subsequent movement of the member is then effective in either causing or controlling the rotation of a ratchet wheel by which the pin-setting lever is carried, the rotation of the ratchet wheel being thus controlled by the extent of movement of the arm.

A further feature of the invention relates to the arrangements for providing the motive power for driving the transmitting gear wheel and for operating the impulse springs. The motive power is provided by a stressed spring and according to this feature of the invention the spring is maintained in a stressed condition during the whole of the operation of the device.

Preferably as soon as the transmitting gear wheel commences to rotate to effect the transmission of impulses, a circuit is closed for a winding device which is thereupon set in operation to stress the spring, the circuit being opened when the spring is fully stressed. The operation of the apparatus with the spring in a substantially fully stressed condition has the advantage that it assists in producing impulses of correct ratio and speed.

Any suitable mechanism may be employed as a winding device and conveniently a ratchet arrangement driven by a self-interrupted magnet is used. Alternatively the spring may be stressed by a self-starting motor.

In applying the modified mechanical impulse repeater to key sending for instance from an operators position in the same or a diiierent exchange, facilities are provided according to a further feature of the invention for cancelling a set up at any time prior to the registration of the last digit. Facilities are also provided according to a further feature of the invention for enabling the re-transmission of impulses to take place as soon as the first digit is registered or only after all the digits are registered. In the first case if the set up is cancelled arrangements are also provided for releasing any automatic switches which may have been set by impulses already transmitted.

Further if the key set is located at another exchange, impulses are transmitted over a junction line between the two exchanges and according to a further feature of the invention, the impulses are received by a relay set which controls a group of magnets in accordancewith the digits transmitted over the junction line. The magnets then control the extent of movement of the arm as explained above.

The invention will be better understood from the following description taken in conjunction with the accompanying drawings comprising Figs. 1 to '7 in which Figs. 1 and 2 show respectively front and rear views of a mechanical impulse repeater modified according to the invention, and Figs, 4 and 3 show cross sectional views thereof along the lines AA and BB respectively of Figs. 1 and 2. Fig. 5 shows the circuit connections of the above mechanism in conjunction with the necessary controlling relays whereby the apparatus is adapted to receive digits keyed up at a distance therefrom and to commence sending out corresponding trains of impulses as soon as the first digit keyed is set up. Figs. 6 and '7 when arranged side by side show the mechanism adapted for use as a straightforward junction system keysender.

Considering now the construction of the mechanism and having a particular reference to Figs. 1-3, a plurality of displaceable pins Ill are carried on a circular ring (Fig. 1) secured to the substantially U shaped mounting plate ll through which the pins project slightly and serve mechanically to effect storage of the keyed up digits, and at the same time to control the length of the outgoing impulse trains.

For the purpose of receiving any of the digits 1-0 which may be keyed, nine so-called digit magnets 12-20 (Fig. 2) are provided and control the travel of the stepped armature extension 2i of the so-called receiving magnet 22. In response to the keying of digits 1-9 the magnets 12-20 are respectively operated and each of their armatures in the operated position provide a stop in the path of the arm 2i as shown by the dotted lines in Fig. 3, while if digit 0 is keyed none of the digit magnets are operated and the arm 2| can effect its fully travel as determined by the stop 23.

When a digit key is depressed the receiving magnet 22 and so-called marking magnet (not shown in Figs. 1-3) are also operated, the armature 24 of the latter magnet being shown in Fig. 2 and the former magnet thereupon moves the arm 2| a distance as determined by the particular digit keyed and in so doing carries the ratchet pawl 25 secured thereto over a corresponding number of teeth on the receiving ratchet wheel 26. as there are displaceable pins, and carries a socalled pin-setting or marking lever 21 (Fig. 3) which under the tension of the leaf spring 28 is normally tilted about its pivot 29 into engagement with one of the pins. A particular pin is accordingly displaced to mark the termination of the last train of impulses transmitted in response to a previous set up. On the main shaft 343 is provided a movable collar 3! with which a forked end 32 (Fig. 2), of the marking magnet armature 24 co-operates. The marking magnet in energising and attracting its armature slides the collar 3! (Fig. 3) inwards along the shaft and the collar by means of prongs (not shown) which project through the receiving disc into engagement with the pin-setting lever, tilt this lever out of engagement with the pins against the action of the spring 28. This particular feature is described in more detail in Patent 2,188,461.

On release of the digit key the particular digit magnet which may have been operated is restored while the receiving magnet 22 is also deenergised. The operating circuit for the marking magnet is also disconnected but it will be understood that until the receiving magnet fully re- This wheel is provided with as many teeth stores its armature, the marking magnet will remain held over a local locking circuit via the receiving magnet interrupter contacts 33 (Fig. 2'). During release of the receiving magnet the ratchet pawl 25 engages with the teeth on the ratchet wheel 26 and this in rotating carries round with it the displaced pin-setting lever 21. When the receiving magnet armature has fully restored the contacts 33 open and release the marking magnet which in turn enables the pinsetting lever 27 to move to the left in Fig. 3 under the action of the spring 28. Lever 21 then pushes the particular displaceable stop pin opposite to which it has been halted into the path of the so-called reset pin 35 attached to but insulated from the transmitting gear Wheel 36. The displaced pin will be a number of pins away from the original displaced pin, this number being equal to the digit keyed. The gear Wheel 36 I meshes with a second gear wheel 3'! with which is associated, in a mamier to be later described, a wound clock spring so that wheel 37 will tend to rotate wheel 35. Rotation of the wheel 36 is prevented however at this instance because the reset pin 35 attached thereto is held by the original displaced pin marking the termination of the previous set up.

Before discussing the actual sending out of the train of impulses corresponding to the keyed up digit, the mechanical operations resulting from the energisation of the transmitting magnet 4| (Fig. 3) will first be considered. This magnet is provided with an armature projection 42 which is insulated from the armature 43 proper, and which when operated moves an insulated spindle 44 extending through the main shaft 33 which is hollow. The insulated spindle 44 in so doing tilts the insulated pin reset lever 4'5 about its pivot 46 and so moves the reset pin 35 to the right. Electrical contact between the spindle 44 and the main shaft is prevented by the use of insulated washers 47 at each end of the spindle, and contact between the spindle and the pin reset lever 45 is prevented by the use of an insulated stud 48 mounted on the left hand end of the spindle. The spindle 44 is electrically connected to the outside oif-normal spring 38 which is insulated from the frame II and co-operates with the inside spring 39 which is electrically connected to the frame. Both these springs are secured to the shaft and they are permitted to close by the insulated buffer 46 moving away from the outside spring 38 as the shaft rotates with the receiving gear wheel 26,. The insulated bufier 48 is secured to an insulated bracket 49 supporting the pin reset lever 45 and it will be understood that after all digits received have been retransmitted and the sending-out wheel 36 has caught up with the receiving wheel. 25, the buffer 46 co-operateswith the outside off-normal spring 38 and lifts it away from the spring 39. The frame H of the mechanism is usually earthed so that when the cit-normal springs close, this earth will extend via the pin 44 and thence to a wiring tag connected to the transmitting magnet armature projection 42. For the purpose of the circuit operation electrical connection must also be made to the reset pin and this is made by way of the pin reset lever and the spring 53 which is tensioned against it and which connects up with another wiring tag.

When the transmitting magnet 4| is energised, which as will be described later in connection with the circuit description, is due to the completion of a circuit from earth by way of the main frame II, the pin reset lever 45 is rotated about its pivot and pushes the reset pin 35 to the right whereby the displaced digit stop pin is returned to its normal position out of the path of the reset pin. It will be understood that the reset pin has a stepped end so that as long as the magnet 4| is energised the steppedportion will remain in engagement with the restored stop pin and so prevent movement of the gear wheel 36. When the magnet is de-energised however, the reset pin is restored to normal by the helical spring 5| wound around it, and the gear wheel 36 is freed whereupon under the influence of the clock spring previously mentioned and through the intermediary of the gear wheel 31 it rotates in the same direction as the receiving ratchet wheel 26 until the reset pin 35 encounters the digit stop pin displaced at the end of the first digit.

As shOwn in Fig. 1 the sending out wheel 36 drives a pinion carrying an impulse cam 52 which during rotation actuates the impulse springs 53 and so transmits a train of impulses correc as regards ratio and speed, and corresponding to the digit keyed. The speed is controlled by an adjustable fly-ball governor 54 of well-known type.

When the reset pin 35 on the gear wheel 36 encounters the stop pin corresponding to the first digit, the rotation is arrested and an electrical circuit is completed over the reset pin and the stop pin against which it is resting to initiate a timing operation for determining the length of the interdigital pause. During this time other digits of the required number will have been keyed up and hence when after expiration of the timing period the magnet 4| is again energised the operation described will be repeated.

When all digits keyed up have been sent out in the form of trains of impulses the gear wheel 36 will catch up with the ratchet wheel 26 when the insulated buffer 40 carried on the former will co-operate with the outer off-normal spring 38 and so open the contact between this spring and the inner off-normal spring 39 to terminate the operations. The pin displaced by the last digit will not be restored and marks the termination of the transmission and at the same time provides a starting position for the next call.

Consideration will now be given to the driving mechanism for the sending-out gear wheel 36 reference being had more particularly to the sectional view of Fig. 4. The wheel 31 can rotate independently of the winding spindle 59 and carries an insulated buffer 51. When this wheel rotates to drive the sending out wheel 36 the bufier 51 moves away from the off-normal springs 55 and 56 secured to winding spindle 59 and so allows them to close. spring 56 connects directly with the spindle 59 and so to earth while the outer spring connects with a pin 58 located within the spindle 59 and insulated therefrom in a similar manner to that in which the spindle 44 is located within and insulated from the main shaft 36. The pin 58 is provided with a metal cap 60 against which the contact metal spring 6| is tensioned. This spring is in turn wired to the break interrupter contacts of the winding magnet 62 (Fig. 2) and thence over the winding of the magnet to battery. As soon as the driving wheel 31 commences to rotate in order to drive the freed impulse sending wheel 36, a self-interrupted driving circuit is therefore completed for the winding magnet 62 and thereupon the ratchet wheel 63 (Figs. 2 and 3) which is carried on and attached to the The inner off-normal winding spindle 59 is rotated on the reverse drive principle under control of the winding magnet armature pawl 64, the detent 65 preventing any backward movement of the wheel 63 each time the winding magnet armature is energised. The wheel 63 is directly coupled to the driving shaft 59 and this in turn has fastened to it the centre of the clock spring 66 (Fig. 4) the other end of which connects with the driving wheel 3'! which can rotate independently of the spindle 59 (Fig. 4).

Immediately the sending out of trains of impulses commences the winding magnet comes into operation to wind up the clock spring and continues to operate until the clock spring is fully wound when the ofi-normal springs carried on the driving spindle 59 will come up against the insulated bufler 51 mounted on the driving wheel 31, and thereupon open and disconnect the driving circuit. By this means the tension of the clock spring throughout the sending out remains substantially constant thereby further assisting the fly-ball governor in producing impulses of correct ratio and speed.

The two operations of receiving keyed up digits and the sending out of corresponding trains of impulses are carried out entirely independently of one another and the whole arrangement is balanced electrically and mechanically in such a manner that it will efficiently respond to and receive incoming digits irrespective of the man-' her and speed at which keying may be eifected, while at the same time due to the arrangements which are made to maintain the clock spring tension substantially constant accurate production of trains of impulses is assured.

The winding up mechanism need not of course be necessarily of the self-interrupted magnet drive type as a self-starting motor could readily be used as an alternative.

Although in the arrangement described the ratchet wheel is directly rotated by the stepped arm during its return movement, it may prove more desirable in practice that the arm should simply control the movement of the ratchet wheel which would be separately driven under either spring, electromagnet or motor control.

Referring now to Fig. 5 this shows the circuit of a typical electromechanical keysender suitable for associating with a P. B. X operators position and adapted to commence sending out trains of impulses immediately the first digit is set up. If after keying up certain or all the digits in a required number the operator should desire to cancel the set-up owing to an error in keying the calling plug will usually be withdrawn for a short period to release the selector train already set up and a cancel key will be operated to cause the keysender quickly to discharge any digits stored therein, the interdigital pause normally provided between digits being suppressed under this condition.

Considering now the circuit operation the digit keys KDIKD9 together with the cancel key CK and the busy lamp BL are assumed to be mounted on the operators position, the keysender proper being mounted in any convenient position. Keys KDl-KD9 are connected respectively to the digit magnets DMI DM9 which have already been described in connection with the mechanical construction of the keysender mechanism while key KDO connects up with the common relay MK via a padding resistance YA of the same resistance as the digit magnets. The receiving ratchet wheel 26 is indicated by the disc R, the pin carrying mounting plate H by the disc P and the sending out gear wheel 36 by the disc S.

On depression of a digit key, relay MK will be operated in series with either one of the digit magnets or resistance YA and in so doing energises the receiving magnet RM and also the marking magnet MM which tilts the pin-setting lever PSL carried by the disc R clear of the pins. On release of the digit key the particular digit magnet which has been operated is restored and relay MK released so that the receiving magnet RM now releases its armature. As already described this armature is arranged to operate the ratchet wheel R on the reverse drive principle and since during the operation the operating pawl will have been carried over a number of teeth on the ratchet wheel corresponding to the digit keyed, on release of the armature the ratchet wheel will be rotated and will carry the pin-setting lever round through a distance of a number of pins corresponding to the digit keyed, the magnet MM being held during this time over a local locking circuit including the interrupter contacts rm of the magnet RM so as to tilt the lever clear of the pins during the whole movement corresponding to the first digit. When the armature of magnet RM completely restores, the pin-setting lever will be positioned opposite the desired pin and the interrupter contacts rm will now open and opens the circuit of the marking magnet MM which in releasing allows the lever to restore thereby pushing the pin into the path of the disc S. The magnet MM in restoring also closes its interrupter contacts mm and since the off-normal springs N of the device will have closed as soon as the disc R rotated away from the disc S, relay ON will now be operated and at armature on3 will light the busy lamp on the operators position to signify that the device is oil-normal and that a digit is stored therein. Earth is new extended over the fixed disc P and the pin displaced to mark the conclusion of the previous operation, insulated reset pin in the disc S, contacts tm, armature 0112, relay P2 to battery. Relay P2 in operating at armature p2 completes an energising circuit for the transmitting magnet TM and this magnet in energising opens its contacts tm and releases relay P'2 which in turn disconnects the magnet energising circuit. This magnet is thus only operated for a period sufiiciently long to move the reset pin and so restore the movable pin in the disc P against which it is resting. The disc S is thus freed from disc P and it now rotates due to the tension in the coiled spring until it comes up against the stop pin in the disc P which was displaced at the end of the first digit. The second and further digits will in the meantime have been keyed and the disc R will have been advanced accordingly to push out further pins corresponding to the digits keyed.

Returning again to the initial operation and release of relay P2, a circuit is also closed at armature onii for the slow-to-release relay IP but relay P2 is operated at the same time and opens the circuit of relay IP before it has time to operate. On the release of relay P2 however after the first energisation of the sending magnet a circuit is again completed to relay 1? which now operates and in turn operates its relief relay IPR. These two relays serve to determine the interdigital pause and it will be seen that after the first digit keyed has been transmitted and the reset pin inthe disc S comes up against the pin displaced by the first digit, relay P2 will be again operated but will be unable to complete an energising circuit for the magnet TM until such time as relays IP and IPR release in turn and enable a circuit to be completed thereto over armatures iprl and p2.

, It will be recalled that the disc S is actually in the form of a gear wheel adapted to drive under control of a suitable adjustable speed governor, a cam controlling the impulsing springs IMP which connect with the outgoing leads l0 and I I.

When all digits keyed have been sent out the disc S catches up the disc R and comes to rest against the final displaced stop pin. In this position the off-normal springs N open and unlock relay ON which extinguishes the busy lamp on the operators position.

In case an error should be made in keying, any digits not yet sent out may be quickly discharged by the operation of the chancel key CK whereupon relay CKR. is operated and looks over its armature clcrl to earth over the ofi-normal springs N and also at armature ckr2 prevents the operation of the pause determining relays IP and IPR so that the device quickly discharges the digits already keyed by suppressing the interdigital pause.

It will be appreciated that there is no necessity to restore the device to normal since it is arranged to resume its operation on the next call from the position it occupies at the termination of the previous one.

The resistances connected across the windings of relays ON and P serve to give these relays a slightly slow-to-release characteristic which enables the general operation of the keysender device to be improved.

Referring now to Figs. 6 and 7, these show a keysender adapted for use in a straightforward junction system, facilities being provided as are usually desired for keying up the digits over four wires, for withholding the sending out until such time as all digits of a number have been keyed up, and also for cancellation 'at any time prior to the keying of the last digit of a number.

For the purpose of this description it will sufiice to say of the straightforward junction system that incoming calls from a distant manual exchange to an automatic area are generally received at a so-called keysending centre at which senders such as that to be described will be located. Direct voice frequency keysending from the distant manual exchange A operator is employed, the junctions from the manual oflice being terminated at the keysending centre on relay sets each of which connects with an automatic exchange selector and which on seizure gain access to one of a plurality of senders in a common group over a sender hunting switch of the wellknown uni-directional type. On seizure of the sender another hunting switch associated therewith is caused to search for and find a free voice frequency tuned relay set whereupon a tone is returned back to the A operator and keying may now proceed. The single or mixed frequencies corresponding to these digits are received on the voice frequency relay set and the corresponding digits are then repeated from the voice frequency relay set into the sender. Assuming that a four digit scheme is being employed, when all four digits of a number have been keyed up and received in the sender, transmission of corresponding trains of loop impulses commences and set the automatic exchange selectors in wellknown mariner.

Considering now the operation of Figs. 6 and '7, on seizure of the sender over the banks of the sender hunter switch, it will be understood that relay BG (Fig. 1) is operated over the P lead by an earth extended from the testing relay associated with the sender hunter switch and this relay thereupon starts up the hunting of the switch PH (Fig. 6) in search of a free voice frequency relay set.

if the outlet on which the test wiper P of switch PH is standing is engaged, earth will be fed back via the wiper, the left-hand low resistance winding of relay K and armatures kl, nd and bgl, magnet interrupter contacts phm to battery Via the high resistance relay GP. This relay now operates (relay K being non-operative under this condition) and at its armature gpl energises the PH switch magnet PHM. The switch is of the reverse drive type and hence no movement of the wipers occurs until the magnet is subsequently de-energised. Magnet PI-IM in energising opens its interrupter contacts phm which release relay GP and this in turn disconnects the circuit to the magnet which deenergises and advances the wipers on to the next set of outlets corresponding to another voice frequency relay set. If the test wiper again encounters a busy earth potential, the same operations will re-occur and relay GP and the magnet PHM will interact with one another so as to rotate the wipers until a free set of outlets is encountered. The P wiper will then pick up a resistance battery potential and relay K will operate over its two windings in series from earth fed over key contacts DBKI and armatures 12513 and 0113, relay GP being unable to operate during this condition owing to the shunting efiect of the low resistance idle marking battery in series with the left hand low resistance winding of relay K. Relay K in operating at its armature kl short-circuits its right hand winding and extends a low resistance guarding and holding potential on to the outlet seized, the circuit to relay GP being disconnected at the same armature, and at armature k2 a circuit is completed to operate relay KA and this relay at its armatures kal and M12 switches the incoming negative and positive leads through over the corresponding wipers of the switch PHI to the voice frequency relay set seized. A tone signal is now returned over these leads to inform the distant A operator that she may commence keying up. Relay KA in operating also at armatures ka3ka,1 connects the digit receiving relays WZ and the cancel signal relay OK to the wipers of the switch PI-I.

When each digit of the required number is keyed one or more of the digit relays are operated over the voice frequency relay set and lock in series with relay DS which also operates. Keying is effected over four wires in well-known manner, the arrangements being such that in response to the keying of digits 1-0, digit relays are operated singly or in combination as follows.

The relay or relays operated then remain locked up until such time as the relay MK operates in series with the digit magnet DMl-DMS or padding resistance YA corresponding to the digit keyed, and opens the locking circuit at armature mkB. As already described the energisation of the digit magnets and/or relay MK in response to the keyed up digits displaces stop pins on the disc P, the receiving and marking magnets RM and MM being energised over armatures mkl and m7c2 respectively. In this instance however sending out does not commence until the predetermined number of digits which the sender is arranged to handle is received, so that in the case of a four digit sender the sending out will not commence until all four digits have been received.

The control of digit transmission may be conveniently efiected by the use of an electromagnetically operated step-by-step switch mecha-' nism SR, 2. known form of which has twelve positions 1-12 position 1 being allocated to the home position and the other positions 2-12 serving for counting purposes, it being appreciated that only seven of these other positions are likely to be required in practice as senders are not usually designed to cater for more than seven digits. The switch in operating step-by-step is arranged to rotate a driving shaft carrying three cams, the first of which serves to operate the oiT-normal contacts SRNI and SRN2 when the switch steps from the home position, the second serves to operate the contacts Al, A2 and A3 in the position corresponding to the storage of the predetermined number" of digitsto be handled and in all subsequent positions up to the home position, i. e., in positions 5-12 in the present instance, while the third cam serves to operate the contacts BI in all positions up to the home position commencing with the position after which contacts AI-A3 were operated. Contacts Bl in the present instance are therefore operated in the positions 6-12 inclusive and serve for the purpose of busying the-sender during the subsequent homing of the stepping switch. The positions in which the various contacts are operated are designated by X in the table at the foot of Fig. 7.

The stepping switch SR is energised each time the marking magnetoperates and closes its contacts mm in response to the keying of a digit and hence when all four digits have been keyed the cam shaft will be rotated to position 5 where contacts AlA3 are operated. Contacts A2 thereupon open the circuit of relay K to release the voice frequency relay set for further common use, and contacts A3 complete an operating circuit for relayON. Relay ON in operating at armature on3 connects an earth on the start lead ST extending from the junction relay set to render it ready to receive trains of impulses and initiates the sending out of the digits keyed in the manner described in connection with Fig. 5 While relay KA is released on release of relay K to connect the impulse springs IMP on to the incoming negative and positive conductors.

When all digits keyed have been transmitted relay ON is released and at armatures onl and OM completes a homing circuit for the stepping relay SR, in the following manner. At armature on! a circuit is completed to operate relay IPR from earth over'the SR switch off-normal contacts SRN2, interrupter contacts 31', armatures onl, and contactsAl'. Relay IPR in operating energises magnet SR at armature iprl and the camshaft is therefore rotated through one stepwhile contacts sr are opened to release relay IPR. Relay IPR-in releasing disconnects the circuit to the magnet SR and the cycle of operations repeats itself until the camshaft reaches the home position 1 when all contacts restore to normal and the driving circuit is disconnected. It will be noted that contacts Bl are operated in positions 6 onwards, and these contacts disconnect the idle marking battery normally extended on to the incoming P lead via the winding of relay BG and resistance YB in parallel so as to signal the junction relay set that'the sender is no longer required and may be cut out of the connection and at the same time to busy the sender until such time as the stepping switch reaches its home position when contacts Bl will close again to once more mark the sender as free. In case the operator keys up one or more of the digits and then wishes to efiect their cancellation she operates her cancel key as a result of which an earth is extended forward over the C bank and wiper to operate relay CK (Fig. 6) which looks overits lower-winding to earth over armature clcl off-normal contacts SRNI of the stepping switch SR. Relay CK in operating releases relay IP at armature R3 and completes at armature c7c4 a driving circuit for the magnet SR in conjunction with relay IPR'whichinteracts with the magnet to rotate the cam shaft step-by-step in a manner already described. As soon as the cam shaft reaches position contacts Al-A3 will be operated and since the keysender mechanism proper will itself be off-normal relay ON will now be operated and at armatures onl and 0112 open the driving circuit to the magnet SR, Relay ON in operating initiates the discharge of the keyed digits which are mechanically stored in the mechanism, the discharge time being kept at a minimum by suppressing the interdigital pause, this being so since no circuit can in this instance be completed for relays IPand IPR. When the mechanism reaches normal, the off-normal springs N open and release relay ON which thereupon recompletes a driving circuit for the magnet SR and interacting relay IPR and the stepping relay is thereupon also restored to its home position.

Returning again to the operation of relay CK this relay in operating at armature ckZ replaces the marking battery normally extended on the incomingP lead over the winding of relay EST by a guard earth potential and this serves to ad- Vance the wipers of the sender hunter switch (not shown) on to the next sender, and at the same time to guard this sender until such time as relay CK restores when the equipment therein becomes normal, If the second sender be engaged the sender hunter will then proceed to hunt for and associate *the distant A operator with another free sender whereupon hunting takes place for another free voice frequency relay set in the manner already described, and the operator may again commence keying up the required number.

The original voice frequency relay set seized is released as soon as the stepping switch SR reaches position 5 and opens its contacts A2 to release relay K while the sender remains 'busied until the stepping relay SR reaches normal when relay CK is released. Relay K in releasing in turn releases relay KA and this connects the impulsing springs IMP to the incoming negative and positive conductors, but since the sender hunter switch will have already been stepped off .the contacts corresponding to these leads the operation of the springs IMP during the discharge of the keyed up digits will be ineffective.

The above method of operation whereby an operator on operating her cancel key is associated with another sender is preferably adopted with the type of sender described since less time will be taken in associating the calling line with another sender than in restoring the stepping relay SR and the keysender mechanism ,to normal.

In certain instances, however, it may be desirable for the operator to hold the sender she has taken into use until such time as thekeyed up digits have been discharged and this could readily be effected by arranging for relay CK in operating to short-circuit the contacts BI in the circuit of relay BG, the contacts A2 in the circuit of relay K and also to disconnect any circuit from the contacts of relay ON on to the start lead ST. Such a facility will be required where B operators are employed at the keysending centre, in which case direct voice frequency keysending from the distant A position will not of course be employed and the banks of the hunter switch PH will connect with keysender B positions. On this type of call the A operator will verbally communicate the number to the incoming B operator who will then perform the keying up and it will be appreciated that if this operator desires to cancel any keyed up digits it is necessary for her to hold the sender and the incoming connection since if the sender hunter switch were caused to associate itself with another senderon operation of the cancel relay CK the incoming call Would in all probability be routed to another B operator and the number would then have to be repeated again to the second B operator.

The keysender mechanism described is provided with sufficient pins to cater for eight digits of ten impulses, which should be suflicient for all present requirements. If necessary the capacity could readily be increased, although of course the provision of extra pins would entail an increase in the size of the mechanism.

The straight-forward junction sender described is applicable to any type of exchange area, it being only necessary to make slight modifications to the stepping switch camshaft to cater for different numbers of routing digits.

Key DBK enables the sender to be out out of service temporarily for test purposes andwhen operated disconnects the idle marking battery from the incoming P lead at contacts DBKI and at the same time disconnects the earth signal to-group busy equipment over lead 10 so as to indicate that the sender is engaged.

I claim:

1. In an impulse sending device comprising a plurality of digit keys, a member adapted to be moved different amounts, a plurality of stops corresponding to said keys for determining the amount of movement of said member, electromagnetic means responsive to the actuation of any one of said digit keys for directly moving said member and for operating the corresponding stop into the path of said member to limit the movement of said member in accordance with the actuated key, a registering device comprising a plurality of settable register pins, means operatively setting onlya particular one of said register pins dependent upon the amount of movement of said member in response to the operation of said member and a transmitting device for transmitting impulses corresponding to said particular set register pin and-actuated digit key.

2. In an impulse sending device comprising a plurality of digit keys, a member adapted to be moved different amounts, an electro-magnet for directly moving said member in its different amounts, a plurality of stops corresponding to said keys for determining the amount of move= ment of said member, a plurality of magnets one for each key, each magnet for controlling one of said stops, an individual circuit for each of said magnets controlled by the corresponding key, circuit means common to said individual circuits responsive to the actuation of any one of said keys for operating said electro-magnet to directly move said member, contact means also responsive to said actuated key for completing the corresponding individual circuit to operate the corresponding one of said magnets to position a corresponding one of said stops in the path of said member to limit the movement of said member in accordance with the actuated key, a register device actuated in response to the operation of said member for registering the amount of movement of said member, and a transmitting device operated in accordance with said registration in the register device to transmit impulses corresponding to the actuated digit key.

3. In an impulse sending device comprising a plurality of digit keys, a member adapted to be moved difierent amounts of movement, an electromagnet responsive to the actuation of any one of said keys for directly moving said memher in its difierent amounts of movement, electromagnetic means also responsive to the actuation of said key for limiting the amount of movement of said member in accordance with the actuated key, a pin-setting lever displaced an amount corresponding to the amount of movement of said member, a particular one of a plurality of pins being set in a registering position in accordance with said displaced lever, and transmitting means actuated in accordance with said set pin in registering position for transmitting impulses corresponding to the actuated digit key.

4. An impulse sending device as claimed in claim 2 in which said movable member comprises an extension arm formed on the armature of said electromagnet and in which said stops for limiting the movement of said member comprises one fixed stop for the greatest amount of movement of said member and the remaining stops being movable by said magnets for lesser amounts of movement of said member.

rality of key sending positions, a set of digit keys at each position, a group of register-senders common to said positions and key sets, and means for operatively associating any one of said regis-' ter-senclers to any one of said positions and its associated key set; each register-sender comprising a plurality of register pins, means for setting certain of said pins to register digits in accordance with the actuated digit keys in the key set at the time operatively associated therewith, means for transmitting impulses, and means whereby said certain set pins stop said transmitting means to divide said transmitted impulses into series of impulses corresponding to the actuated digit keys.

8. A transmitting system as claimed in claim 7 including a trunk line for operatively associating any register-sender with any one of said positions and its associated key set, and a coding device for transmitting coded pulses over said trunk line to control said means for setting certain of said pins to register digits in accordance with the actuated digit keys.

9. A transmitting system as claimed in claim 7 including a cancel key at each of said key sets, and means responsive to the operation of said cancel key for restoring the register-sender which at the time is operatively associated therewith and for operatively associating another register-sender with the particular key set in use.

10. A transmitting system as claimed in claim '7 including means for introducing an interdigital pause between each series of transmitted impulses, and means operative in case of an error for restoring said registersender to normal and for suppressing said interdigital pause.

CECIL ROBERT WOODLAND. JOHN WILLIAM MCCLEW. ERIC INNES HOUGHTON. 

